1. Field of the Invention
The invention herein disclosed relates to a method for on-site treatment of wet drill cuttings produced by earth-boring operations. In particular it relates to means for on-site dehydration and binding of potential detrimental liquids wetting such cuttings. With more particularity the method herein disclosed and claimed provides a means for pacification of potential detrimental liquids wetting such cuttings without the necessity of using a reserve pit, reinjection of the cuttings or transportation of the cuttings for off-site treatment or disposal. The method disclosed is particularly well suited for use at environmentally sensitive drilling locations, where “zero-discharge” regulations are applicable.
2. Description of Related Art
In the field of earth-boring operations cuttings from the borehole (“drill cuttings”) are brought to the surface. Such cuttings are recognized to present environmental challenges. They may contain some oils and greases. When brought to the surface they will inevitably be wet with drilling fluid (commonly called “drilling mud” or simply “mud”). Said mud will more often than not contain a variety of substances which are considered detrimental to the environment. Some of these salts, such as chloride and other salts, may have been intentionally added to the mud to impart various properties, such as additional weight, thereto. The mud may have also picked up various substances while drilling through various downhole formations. What to do with cuttings wetted with substances that are considered detrimental to the environment presents the problem. The invention disclosed and claimed herein does not attempt to address the problem of radioactive cuttings, but is directed to “ordinary” cuttings, those which are wetted with drilling fluid containing substances considered detrimental to the environment, including but not limited to some hydrocarbon substances.
Prior art teaches various means to address this problem. In many applications the problem is addressed by use of a reserve pit. As those skilled in the art of drilling will be aware a reserve pit commonly constitutes a diked area, where not only drill cuttings, but other potentially contaminated solids and fluids are temporarily stored during drilling, but typically, by regulation, must be cleaned up at the conclusion of drilling. This method of addressing the problem has various limitations. Increasingly, in environmentally sensitive areas, use of reserve pits is prohibited. Physical limitations of a drilling site may also preclude use of a reserve pit. Even when use of a reserve pit is not otherwise precluded, pit closure and clean up presents many issues, including separation of hydrocarbons, water and solids and appropriate treatment, if possible, for disposal on-site or for transport, treatment and/or disposal at an approved disposal site.
Prior art also teaches that contaminated drilling cuttings may, in some cases, be disposed of by reinjection technology. As those skilled in the art will know this will generally comprise collection of the cuttings, grinding to a sufficiently small size so that they may be included in a slurry, and disposal of the cuttings by pumping the slurry into an earth bore, or a designated zone of an earth bore. Practice of this method involves use of an earth bore or a zone thereof, which is not always available. In reinjection care must be taken so that certain underground formations are not damaged. In certain areas reinjection is not permitted. Practice of the method involves use of substantial, relatively complex equipment, for which space may not always be available and constitutes an extra expense.
Prior art also discloses that wet, potentially contaminated drill cuttings may also be handled by transportation away from the drilling site, for treatment or disposal elsewhere, including but not limited to disposal at an authorized disposal facility. However, authorized treatment and/or disposal facilities are not always located nearby. While transportation for treatment and disposal even short distances poses increased expenses (including but not necessarily limited to shipping costs, increased fuel consumption, increased road maintenance, treatment and disposal fees), transportation long distances worsens the problem.
Prior art also teaches that drill cuttings may be washed clean of contaminants, after which they may be handled as an environmentally safe substance. While this method proposes a solution with respect to the drill cuttings themselves, it poses another, namely how to treat, dispose or otherwise handle the liquids which were used to wash them. Accordingly this proposed solution has not been generally accepted.
As exploration for minerals expands into a greater number of areas that have been declared environmentally sensitive areas, sometimes referred to as “zero-discharge” sites, which areas may be more remote from established transportation routes, none of the above means may be economically suitable for handling drill cuttings contaminated with drilling fluid. In such areas exploration for minerals cannot presently be conducted.
The invention described and claimed is directed to avoiding some of the shortcomings of each of the above described methods of handling drill cuttings contaminated with drilling fluids. In accordance with the invention, drill cuttings contaminated with drilling fluids may be treated effectively and economically, at the drilling site, by a process that binds the water of the drilling fluid and the contaminants therein into a solid structure which is sufficiently non-leaching to satisfy current environmental regulations. The treated drilling cuttings may be disposed of or used as a non-environmentally hazardous substance. They are disclosed to be particularly useful in the “permatizing” of a drilling location for subsequent mineral production therefrom.